<?php 

    define('HOST', "localhost");
    define('USER', "php_user");
    define('PASS', "PHP123");
    define('DB_NAME', "php_test_db");   
    print_r(USER);     
    
    $db_connection = mysqli_connect(`HOST` , `USER`, `PASS`, `DB_NAME`) or die("Error" . mysqli_error($db_connection));;

?>
